1. Field of the Invention
The present invention relates in general to a refrigerant transporting hose and a connector for such a hose, and more particularly to a hose suitable for use as a refrigerant conduit for an automotive cooler or air conditioner, and a connector for connecting such a refrigerant transporting hose.
2. Discussion of the Prior Art
A hose having a three-layered integral laminar structure is known as a conduit for transporting a refrigerant such as flon gas (fluorohydrocarbon and chlorofluorohydrocarbon). This three-layered hose consists of an inner rubber layer, an outer rubber layer disposed outwardly of the inner rubber layer, and a reinforcing fiber layer interposed between the inner and outer rubber layers. The inner rubber layer is generally formed of acrylonitrile-butadiene copolymer rubber (NBR) or chlorosulphonated polyethylene rubber (CSM), while the reinforcing fiber layer has a mesh structure formed by braided organic fiber yarn such as polyester fiber, rayon fiber, or nylon fiber. The outer rubber layer is formed of an elastomer (EPDM) consisting of a copolymer of ethylene, propylene and diene, or chloroprene rubber (CR). The outer rubber layer has spiking holes formed from its surface down to the reinforcing fiber layer, so that the flon gas which has permeated through the inner rubber tube may escape outside the hose, thereby preventing the gas from remaining between the adjacent layers. The flon gas remaining between the adjacent layers may cause local expansion at the interfaces of the adjacent layers, resulting in undesired separation of the layers from each other.
This type of hose whose layers are formed solely of rubber materials except for the reinforcing fiber layer exhibits a high degree of flexibility, and is accordingly easy to handle when the hose is installed in place as a conduit. Further, the known hose indicated above has a high sealing effect or fluid-tightness with respect to a connector nipple or other hose joint. However, since a rubber material, in particular, NBR and CSM commonly used for the inner rubber layer, has some degree of gas permeability, the known hose tends to suffer from leakage of flon gas or other refrigerant, when the refrigerant has a relatively low molecular weight. Namely, the conventional hose which consists principally of such rubber materials permits the refrigerant gas to permeate through its wall and leaks out, whereby the amount of the refrigerant circulating in a refrigerating system is gradually reduced, leading to reduction in the cooling capacity of the system. To maintain the desired cooling capacity of the system for a prolonged period of time, therefore, the system should be re-charged by the refrigerant gas, at relatively short intervals. Thus, the known refrigerant transporting hose has a maintenance problem. Further, the destruction of the ozone layer of the earth atmosphere by flon has been an environmental problem these days. In this respect, there has been a need for improving the gas impermeability or resistance to gas permeation of the refrigerant transporting hose.
In an attempt to improve the refrigerant impermeability of the hose, it has been proposed to provide the inner tube of the hose with a resin layer made of a resin material which exhibits high refrigerant impermeability. For example, a hose whose inner tube includes a resin layer formed of a polyamide resin such as nylon 6, nylon 66 or a copolymer thereof is proposed. While this hose is considerably improved in the refrigerant impermeability, the hose suffers from insufficient flexibility due to excessively high hardness or rigidity of the polyamide resin. If the thickness of the polyamide resin layer is reduced so as to increase the flexibility, the refrigerant impermeability of the hose is undesirably deteriorated.
As discussed above, the known refrigerant transporting hoses have both an advantage and a disadvantage and are not practically satisfactory in quality, particularly, in view of the recent increasing need for further improvement in the refrigerant impermeability.